Figure 5
figure



June 11, 1968 G. RUMBERGER Re. 26,402

SEALABLE OVERLAY CARTON Original Fned Aug. 23 1961 /i/ e #21 /32 /34\/33 N FIGURE 7 INVENTOR FIGURE 8 United States Patent 26,402 SEALABLEOVERLAP CARTON George G. Rumberger, Portage, Mich., assignor, by mesneassignments, to Brown Company, New York, N.Y., a

corporation of Delaware Original No. 3,194,473, dated July 13, 1965,Ser. No.

133.420, Aug. 23, 1961. Application for reissue Nov. 24,

1967, Ser. No. 689,735

14 Claims. (Cl. 229-47) Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE Carton blanks and cartons formed therefromhaving an inner flap, fall outer flap, and intermediate flap hinged to acarton panel opposite the panel to which the outer flap is hinged, theintermediate flap being recessed along an edge so as to be narrower thansaid outer flap and provide an area of overhang of said intermediateflap by said outer flap along a transverse side of said intermediateflap perpendicular to its hinge line, at least one of said flapsprovided with adhesive adapted to be disposed and activated in the areaof overhang, the adhesive securing the outer flap to the inner flap inthe area of overhang. Preferably the carton is constructed of laminatedsheet material with said adhesive being provided from between the pliesof said laminated sheet material.

The present invention relates to carton blanks, cartons, and a method offorming sealed cartons, and is more particularly concerned with cartonblanks in which the adhesive for sealing of the carton erected from suchblank is carried by or indigenous to the material of construction of thecarton blank, with erected and sealed cartons formed from such blanks,and with a novel method of forming such scaled cartons. Because theadhesive is either carried by or indigenous to the material ofconstruction of the carton blanks of the invention and cartons formedtherefrom in the area of the closure flaps, there is no need to provideadhesive extraneously. Because the intermediate closure flap of thecarton is recessed at its edges so that the outer flap of the cartonoverlies the intermediate flap along its edges upon folding of theflaps, the carton is sometimes referred to herein as an overlap carton.The particular cartons with which the invention is concerned, uponclosure of the same, therefore, have an area of opposed facingrelationship between the outer flap and the inner flap or flaps in thearea of overhang of the intermediate flap by the outer flap, and carryadhesive which is provided and activated in place at least in the saidarea of overhang, but which adhesive is substantially and usuallycompletely absent from the exterior exposed faces of the scaled carton.

Numerous cartons have been proposed and adopted in practice which areprovided on at least one end with closure flaps, adapted to be foldedover and adhesivcly secured. In many instances, the carton is providedwith similar flaps at both ends. In such cartons, at one or both ends. acarton closure is formed by adhcsively securing flaps which lie with thesurface of one flap upon the surface of another flap, with certain ofthe flaps presenting free or cut edge surfaces along opposite edges ofthe closure. This is true whether the shape of the carton isconventionally square or rectangular, or triangular, pentagonal, orhexagonal in its configuration, or any one of numerous additional shapesin which such type cartons are already known or can be made. Such typesof cartons Re. 26,402 Reissued June 11, 1968 "ice may be sealed byconventional gluing, and in some cases may be provided with hot melt orother adhesives on the inner surfaces of the outer or intermediateflaps, for sealing of the carton upon the application of heat and/orpressure thereto. Other cartons of this type have been conventionallysealed with glue and have thereafter been dipped in molten paraflin orother wax, wax and rubber mixtures, or other sealing and proofingsubstances, for purposes of proofing and sealing the ends of the cartonsagainst watervapor transmission, since it is at the carton ends whereclosure is effected by folding the flaps upon each other that thegreatest leakage is likely to occur. While there can be no questionabout the initial proofness or seal of cartons which are wax-dipped,this is indeed an untidy and uneconomic operation and not one which canreadily be accomplished in or in conjunction with rapidlymovingpackaging equipment, naturally involving at least one additional stepafter completion of the usual packaging operation, depending uponwhether the entire carton is dipped as a whole or whether the ends aredipped separately. In addition, dipped cartons are subject to abrasionor rupture of the coating material not only throughout the entire coatedarea but especially along free edges of flaps, and rupture of thecoating material along a surface or edge of the carton adjoining anyarea of overlap of one flap by another flap also tends to rup turecoating material collected therein due to stresses on the exposedcoating which are conveyed from the exterior via the integral mass ofcoating material.

Moreover, wax dipped or coated cartons leave much to be desired by wayof their appearance and, in handling, considerable amounts of coatingprovided by a clipping, painting, or spraying operation frequently chipoff and cause displeasure, discomfort, annoyance and an unsightlyappearance when coming into contact with the contained product or withhands, clothing, or personal effects of the consumer.

Attempts are therefore made to avoid dipping operations whereverpossible, and resort has been had to overwrapping of cartons and/or toinnerwrapping of products contained therein to obviate its use. Althoughsatisfactory in many applications, these approaches also involveseparate steps or operations and leave much to be desired.

It would be highly desirable to have available a carton which could berapidly and effectively sealed, especially on rapidly-moving cartonerecting and filling equipment as ordinarily employed in the packagingindustry, which would be equally adaptable to both leakproof andnonleakproof closures, and which would, when a proofed or evenhermetically sealed carton was desired, not be subicct to thedisadvantages attendant upon the use of previous procedures includinginncrwrapping, ovcrwrapping, or dipping.

It is therefore an object of the present invention to provide cartonswhich carry on the materials of their construction or as an indigenouspart thereof their own sealing adhesive, and which are not subject toany of the disadvantages hereinbefore mentioned. Another object of thepresent invention is to provide cartons which are sealable by heatand/or pressure or the like to provide a more satisfactory seal of theclosure flaps than previously attained by known methods or possible withpreviously known cartons of the same or similar type, and in which theintermediate flap underlying the outer flap is completely sealed oflfrom contact with the exterior. An additional object is to provideedge-sealing cartons which upon sealing by the application of heatand/or pressure do not bow in because of the application of heat and/orpressure as is commonly experienced with such type sealing cartons. Afurther object of the invention is to provide such cartons which sealreadily and effectively upon the application of heat and/or pressure dueto the fact that, especially when heat is employed, only one layer ofcarton thickness must be penetrated to effectuate the edge seal. A stillfurther obpect of the invention is the provision of carton blanks fromwhich such cartons are produced, and still an additional object is theprovision of such carton blanks and cartons formed therefrom which arecharacterized by an area of overlap between the outer and intermediatecarton flap closure members and in which the adhesive necessary for thesealing of such cartons is either carried by the material ofconstruction of said flaps or indigenous thereto and adapted to bedispOscd in place at least in the area of overlap of the intermediateflap by the outer flap of the carton and activated upon the applicationof either heat or pressure or both. A further object is the provision ofa novel method of sealing such cartons as aforesaid. Other objects ofthe invention will become apparent to one skilled in the art and stillother objects of the invention will become apparent hereinafter.

It has now been found that the foregoing and additional objects of theinvention are accomplished by the provision of carton blanks and cartonsformed therefrom, in which the intermediate closure flap is recessed,relieved, or cut away at its edges with reference to the top or outerclosure flap, and in which the top and/or inner flap or flaps (whichinner flap or flaps when folded in closing the carton will lie beneaththe intermediate flap) are provided with a coating of thermoplastic,heat-sealing, or pressure-sensitive adhesive at least in the area inwhich the outer tlnp overhangs the intermediate flap of the car ton uponcarton closure. '1 he adhesive may also be carried within the materialof construction of the said intermediate fiap and adapted to be extrudedoutwardly upon the application of heat or heat and pressure and thislatter embodiment, in which the adhesive is a thermoplastic adhesivelnrninant disposed within the intermediate flap member, constitutes apreferred embodiment of the invention. An especially preferredembodiment of the invention resides in such latter type of heat-sealingarrangement wherein the entire carton body is constructed of laminatedsheet material and in which the closure is effected by extrusion of theheabsealing thermoplastic laminant adhesive from the recessed cut edgesof the intermediate flap of the carton in the area of overhang of saidintermediate flap by the outer flap.

I have discovered that by providing a novel combination of a cartonblank wherein the edges of the intermediate closure flap are recessed, acarton structure is provided which, when erected and closed, ischaracterized by a recess along opposite sides of the closure, andwhereby, upon closing of the carton, the face of the outer flaps comesinto opposing relationship with the inner flap or flaps along therecessed edges of the intermediate flap and that, by providing inaddition to the said area of overhang an adhesive. either carried on thesurface of one or more of said opposing flaps at least in the said areaof overhang or adapted to be provided in said area of overhang byextrusion from the recessed edges of said intermediate flap, and in anycase adapted to be activated upon the application of adhesive-activatingconditions, such as heat and/or pressure, the outer or top flap issealed directly to the inner flap or flaps in the said area of overhang,thereby also sealing Off the cut edges of the recessed intermediateflap, without substantially any of the said adhesive coming into contactwith or being disposed or present on the exposed exterior faces of thecarton. This enables employment of the carton in ordinary packagingequipment and provides a rapid and effective means of sealing the sameby the mere application of heat and subsequent cooling in the case ofthe thermoplastic or heat-sealing adhesives, either along or togetherwith pressure, or the application of pressure alone in cases wherepressure-sensitive adhesives are employed.

lti

Another obvious advantage of the invention is its economy, in that onlyso much adhesive is employed as is required to effectuate the seal,especially significant Where leakproof canons are in question, in whichcase the saving in both time and materials as contrasted to dipping isclearly apparent.

The process of heat sealing the edges of the carton by extrusion ofadhesive from the recessed edges of the intermediate flap isparticularly advantageous in that it ohviates the use of a mandrel forsealing. The number of cartons which can thus be heat sealed in a giventime is greatly increased over that previously attainable in view of thefact that the maximum number of cartons which can be sealed per minuteusing a mandrel is about ninety, while on standard packaging machinerywithout the necessity of employing a mandrel the number of cartons whichcan be sealed per minute is on the order of four hundred. In addition,heat-scaling by effecting a caulking from the cut ecgcs of a recessedintermediate flap, by the extrusion of thermoplastic latninant adhesivetherefrom, not only presents a clearly novel concept in the edge sealingof cartons generally, but also provides an effective method of scalingthe cut edges of the intermediate flap, and is moreover characterized bthe absence of warping or bowing of the carton which is frequentlyencountered using heat'senling cartons and especially when sealingwithout a mandrel is attempted.

Elimination of warping or bowing can also be effected by the provisionof a satisfactory thickness of thermoin i n ni i the tip or outerclosure flap, said iltfcl'f d being at least about as t i termediatetl'l r and at any rate at l. t a great as the spite separating the outerflap from the inner Mn or flaps.

pur :s of fu ther illustmting the invention, when a cart n 1-: ct sodand adhesively secured according to ordinary practice. an inlermcdintcflap lies above at least one, and usually above a pair, of shorter flapsand is covered by an outer flap. The intermediate and outer flapspresent cut edges at opposite sides of the carton closure, which areusually coterminous since the intermediate and outer flaps areordinarily of equal width. Under ordinary circumstances, the adhesiveused in retaining the flaps in their closed positions may or may not berelied upon to effect a sealing of the carton, but for a leakproofcondition the product is ordinarily innerwrappcd, or the carton dippedor over-wrapped. If dipped, sprayed, or painted, as already pointed out,a very slight rupture of the thin skin of wax or other material employeddestroys the sealed character of the container even in crevices orcracks where, as already pointed out, the coating material isdependently subj..ct to rupture upon rupture of the integral cartoncoating at the exterior of the carton adjacent thereto. This is not theease with the method and products of the present invention, since theadhesive sealing medium is retained entirely or substantially entirelywithin the recess bridging the gap between the outer flap and the innerflap and uniting them together in sealed relationship, and thus the bondbetween them in the area of overlap is considerably less subject torupture from the application of forces to the outer faces of the cartonadjacent thereto. where according to the present invention no orsubstantially no adhesive exists.

According to the invention, the thickness of the sealing adhesiveprovided in situ in the recess between the outer flap and the inner flapor flaps is sufficient to provide strength and resistance to handlingand scuffing so that abrasions normally expected during use cannotdestroy the seal which effectively bonds the inner surface of the outerclosure flap to the upper surface of the inner llap or flaps, adhesivethickness being ordinarily equivalent to the thickness of the spaceseparating the outer flap from the inner flap.

Reference is now made to the accompanying drawings which show exemplaryembodiments of certain carton blank and carton constructions andarrangements of parts which may be employed according to the presentinvention without any limitation of the invention thereto, wherein thesame numerals refer to the same parts, similar parts of differentfigures are denoted by like numbers except for a hundred place digit,and wherein:

FIGURE 1 is an enlarged crossscctional view of a portion of a laminatedsheet material which is one type of sheet material utilizable accordingto the invention.

FIGURE 2 is a partial plan view showing the inside or heat sealing sideof a carton blank embodying the present invention.

FIGURE 3 is a partial plan view of the heat-sealing side of anothercarton blank embodying the invention.

FIGURE 4 is a partial plan view of the heabsealing side of a furthercarton blank embodying the invention.

FIGURE 5 is a top or bottom view of any erected and sealed cartonconstructed in accord with the invention.

FIGURE 6 is an C.'-.'3":'"Z.t0d cross-ssctional view on line VIVI ofFIGURE 3, considering FIGURE 5 a top view, showing one form of theerected and sealed carton, having been erected from the carton blank ofFIGURE 2.

FIGURES 7 and 8 are exaggerated cross-sectional views on lines VIIVlland VllI-VIII of FIGURE 5, respectively, considering FlGURlE 5 a topview, showing other forms of the erected and scaled carton embodying theinvention, having respectively been erected from the carton blanks ofFiGURES 3 and 4.

Referring now to the drawings, FIGURE 1 is an enlarged cross-sectionalview of a portion of a laminated sheet material til, which is one formof sheet material utilizable in constructing cartons according to thepresent invention, as it might be formed by laminating a fifty pound perream (24 x 36-5Ut)) 020035 inch thick dry waxed paper shcet ii to a.(JiZ inch thick paperboard sheet 13 with .0065 inch of thermoplasticlaminating adhesive 12.

FIGURE 2 is a partial plan view of the inner or heatsenling side of acarton blank 20 of generally rectangular dimensions cut from laminatedsheet material 10' with thinner or paper ply 11 facing the viewer. Thecarton blank includes rectangular front face panel 21, back face panel22, and right hand and left hand end panels 23 and 24. The blank alsoincludes front top flap 31, back top tlap 32, and right hand and lefthand end flaps 33 and 34. Also seen in FIGURE 2 are glue flap and itsextension 35. Face and end panels 21 through 24 are all integral andjoined to each other along parallel transvese score lines 4'7 through49, and front face panel 21 is also integral with and joined to glueflap 25 along parallel transverse score line 46. Face and end panels 21through 24 are all integral with and joined to their respective topllaps 31 through 34 along longitudinal score lines 55 through 58.Extension 35' is integral with and joined to glue flap 25 along scoreline 59, which is an extension of longitudinal score lines through 58,all of which are extensions of each other. Transverse cuts are providedbetween the edge of blank 29 and the longi tudinal fold line formed byscore lines 55 through 59 between front top flap 31 and end flap 33,between front top flap 31 and extension 35, and between back top flap 32and end flaps 33 and 34, to permit all flaps to be folded inwardly atright angles with respect to their adjacent panels. Back top flap 32 isrecessed or cut away at its lateral edges 62 and 63 so as to be ofdimini hed width with respect to front top flap 31 at its longitudinaledge :.nd is further provided with a curved reach in each of its lateraledges as at 64 so as to impart a full width to back top flap 32,equivalent to the width of back face panel 22, at its juncture therewithalong score line 56. Back top flap 32 by virtue of its recessed edgesand diminished width is therefore not only of diminished width but alsoarea with respect to front top flap 31,

which will accordingly overhang fiap 32 at its lateral edges when thecarton is erected and closed. As shown, top flap 31 carries a layer ofthermoplastic adhesive 12a in the area bordering its longitudinal edgefor sealing of this edge to the upper surface of flap 32 adjacent scoreline 56.

FlGUl-{E 3 is a partial plan view of another form of carton blankembodying the invention. This carton blank -26 is constructed fromsingle-ply paperboard sheet material 11d, of which inner or heat-sealingside 111 is sl'iown t 1g the viewer. The blank is similar to that shownin HGURE 3, being provided with rectangular lace and end panels 121through 124, top flaps 131, through 134, glue flap 125 and extension135, parallel c score lines 146 through 149 along which all ious panelsand glue flaps are both integral and and longitudinal score lines 155through 153 g which the top flaps are joined to their respective panelsand 159 along which extension is joined to glue flap 125, said scoreline 159- being an extension of score lines 155 through 153, all ofwhich are extensions other. The blank is provided with transverse cuts:1 the edge and the longitu inal fold line formed re lines 155 through159 between top flaps 131 and between top flap 131 and extension 135,and been back top flap 132 and end flaps 133 and 134, to w the variousflaps to be folded inwardly at right with respect to their adjacentpanels. Back top flap is again of diminished width and area with respectto front top flap 131, being recessed at its edges 162 and 163 and beingangled along each of said edges at 164, so as to be of such diminishedwidth throughout substantially its entire lateral reach except at itsjuncture with back face panel 122 along score line 156. Front top fiapMI is shown provided with a layer of thermoplastic adhesive 112throughout substantially its entire area.

FIGURE 4 is again a partial plan view of a carton blank 226, in accordwith the invention. very similar to that shown in FIGURES 2 and 3,except that it is formed from a two-ply papenpaperboard sheet material210, the thinner or paper ply 211 of which faces the viewer and thethicker or paperboard ply 213 of which is not shown. Pace and end panels221 through 224 of rectangular nature are integral with and joined toeach other along pa .illel transverse score lines 247 through 249 andglue tlap 225 is integral with and joined to front face panel 231 alongscore line 246. Top flaps 231 through 234 are all joined to theirrespective face and end panels 221 through 224 along longitudinal scorelines 255 through 258 and glue flap 225 is integral with and joined toits extension 235 along score line 259, said score line 259 being anextension of score lines 255 through 258, all of '1 are extensions ofeach other. Transverse cuts are pro. ded from the edge of the blank tothe longitudinal fold line formed by score lines 255 through 259 betweentop flaps 231 and 233, between top flap 231 and extension 235, andbetween back top flap 232 and end flaps 233 and 234, to allow the flapsto be folded inwardly at right es with respect to their adjacent panels.Back to fiap is of diminished width and lateral reach with respect tofront top flap 231, being recessed at each of its edges 262 and 263 asindicated at 264 so as also to be of diminished area with respect to topflap 231, which will accordingly overhang flap 232 at three edges. inparticular each of lateral edges 252 and 263 to the extent cated by 264,when the carton is erected and closed. Back top flap 232 is likewise ofdiminished width with respect to its adjacent back face panel 222 withwhich it is integral and joined along score line 256. Front top flap 231is shown provided with a coating of thermopl ie adh sive 212 in theareas immediately adjacent its lz'tcral and longitudinal edges, so as toleave only a central area immediately adjacent front face panel 221along score line 255 without such coating 212.

FIGURE is a top or bottom view of any erected and sealed cartonconstructed in accord with the invention and is included solely forpurposes of providing a line upon which the cross-sectional views ofsubsequent figures may be taken. When viewed as in FIGURE 5, an erectedand scaled carton according to the present invention has substantiallyno different appearance than any other conventional carton, the top orbottom 80 and front face panel 81 of any such carton being shown andindicated in FIGURE 5.

FIGURE 6 is an exaggerated partial cross-sectional view on line Vl-VI ofFIGURE 5, considering FiG- URE 5 a top view, showing one version of anerected and sealed carton embodying the invention. having been erectedfrom the carton blank of FIGURE 2 and sealed by the application of heator heat and pressure. As viewed in FIGURE 6, front top flap 31, back topflap 32, and end flaps 33 and 34 are visible. Front top flap 31 overliesback top flap 32 which in turn overlies end flaps 33 and 34. Right handend panel 23 is shown attached to end flap 33. Thermoplastic laminantadhesive 12 has extruded outwardly from the recessed edge 63 of back topflap 32, thereby forming a bond of thermoplastic adhesive laminant 12directly between bottom ply 11 of top flap 31 and top ply 13 of end flap33 in the area of overhang, and also sealing off the cut edge 63 of backtop flap 32 against wicking. Extension of thermoplastic laminantadhesive 12 out of the cut edge of front top flap 31 has also sealed offthe plies of sheet material at this cut edge against wicking.

FIGURE 7 shows an exaggerated partial CroSs-sectional view on lineV1I-VII of FIGURE 5, considering FIGURE 5 a top view, of another cartonerected and sealed by the application of heat or heat and pressure, thistime having been erected from the carton blank of FIGURE 3. As viewed inFIGURE 7, front top flap 131 of single-ply sheet material 110 overliesback top flap 132 and is adhered thereto by layer of thermoplasticadhesive 112 carried thereon, while back top flap 132 in turn overliesend flaps 133 and 134. Right hand end panel 123 is shown attached toadjacent end flap 133. Thermoplastic adhesive 112 coated on front topflap 131 bonds said flap to end flap 133 in the area of overhang of backtop flap 132 by top flap 131 which exists due to recessed edge 163 ofback top flap 132, also sealing off cut edge 163 against wicking. Thus,an integral bonding between front top flap 131 and end flap 133 has beeneffected.

FIGURE 8 shows an exaggerated partial cross-sectional view on lineVIIIVIII of FIGURE 5, considering FIG- URE 5 a top view of, another formof carton erected from the carton blank of FIGURE 4 and sealed by theapplication of heat or heat and pressure. As viewed in FIGURE 8, fronttop flap 231 overlies back top flap 232 and is adhered thereto bythermoplastic adhesive 212. Back top flap 232 in turn overlies end flaps233 and 234,

which latter is integral with and joined to right hand end panel 223,also shown. Since the material of construction in this case involvespaper ply 211 and paperboard ply 213, both plies are shown.Thermoplastic adhesive 212 coated on inner ply 211 of front top flap 231forms a direct bond to the upper ply 213 of end flap 233 in the area ofoverhang of back top flap 232 by front top flap 231 which exists becauseof recessed edge 263 of back top flap 232. The thermoplastic adhesive212 in the area of overhang also effectively seals off cut edge 2&3 ofback top flap 232 against wicking.

In operation, a carton blank is first produced from suitable cartonstock, such as paper or paperboard or the like, and preferably, but notnecessarily, of laminated sheet materials such as shown in FIGURE 1, thecarton blank thus produced having a configuration the same as or similarto those shown in FIGURES 2, 3 and 4. Where the adhesive is to bedisposed only upon the surface of the flaps, it may be disposed upon anyor all of them as previously indicated, but at any rate it will bedisposed either upon the inner flap or flaps or upon the outer flap inthe area of overlap of the intermediate flap by top flap, or upon bothinner and outer flaps in this area. When a more complete seal isdesired, and less bowing, the adhesive is disposed upon the surfaces ofboth end and outer flaps in the area of their opposed fac ingrelationship in the area of overlap of the intermediate flap by theouter flap.

In order to provide sufficient adhesive in the area of overhang,advantage may be taken of the fact that adhesive applied to the uppersurface of an intermediate flap or the inner surface of a top flap, orboth, may be chosen of suflicient fluidity to flow, upon application ofactivating conditions, to the space provided between the top and innerflaps in the area of overhang of the intermediate flap, thereby to fillthis space. Moreover, the inner flap may be, and in some casespreferably is, shortened so as to correspond upon folding with thecontour of the recessed edge of the intermediate flap, or substantiallyso, or it may even be embossed or suitably eontoured so as to provide arecess for the relieved edge of the intermediate flap where said innerfiap underlies the said intermediate flap, whereby the opposed surfacesof the inner and outer flaps are brought closer together.

When laminated sheet material is employed, the adhesive is provided inthe area of overlap by extrusion from the recessed edges of theintermediate flap to a sufficient thickness so that bowing is notexperienced. For some purposes, such as tacking of a carton, it isentirely sufficient that the seal be present only in the area ofoverlap. For other purposes requiring more complete scaling, adhesive isalso disposed on the inner ply of the top or outer flap, as shown inFIGURE 2, or a thermoplastic or heat-sealing or pressure-sen itiveadhesive may be distributed upon a part or all of the surface of theintermediate recessed fiap which will be upwardly disposed upon closingof the carton, or upon the inner surface of the outer flap which will beinwardly disposed upon closureof the carton, but will ordinarily bedisposed only on the surfaceof the intermediate flap adjacent the scoreline along which the intermediate flap adjoins its face panel, or alongthe outer edge of the outer flap, so as to effectively provide a sealbetween the intermediate flap and the top flap adjacent the score linealong which the intermediate flap adjoins its face panel upon theapplication of heat or heat and pressure. Although the adhesive employedfor interfacial bonding of the intermediate and top flaps is usually ofconsiderably less thickness than the thickness of the laminant in thelaminated sheet material employed, this is not critical since, uponsealing by extrusion of thermoplastic adhesive from the recessed edgesof the intermediate llap, especially when heat and pressure areemployed, the thickness of the intermediate flap is somewhat reduced andthe extruded adhesive in the recessed area readily attains a thicknessapproximating that of the somewhat flattened intermediate flap.

The basic seal between the surfaces of the recessed intermediate flapand the outer flap, where required, may in some cases even be effectedby the employment of conventional glue, leaving the sealing between theouter flap and the inner flap or flaps in the area of overhang to beeffected by the application of heat and/or heat and pressure to causeextrusion of the laminant from the recessed edges of the intermediateflap, or by activation of surface-carried adhesive in the area ofoverhang. When present in areas other than the area of overhang, thethickness of any adhesive on the surface of any flap or flaps ispreferably but not necessarily of a considerably lesser thickness thanthe combined thickness of surfacc-carried adhesive in the area ofoverhang, when surface carried adhesives are employed.

After provision of the carton blank with suitably disposed adhesive,either carried by or disposed within the material of construction of theintermediate fiap, a suitable carton body is erected from the cartonblank in the usual manner'by securing an end and face panel thereof toform a tube, and the carton then closed by folding in the end flap orflaps, folding the recessed intermediate flap in upon the end flaps, andfolding the top or outer flap in upon the intermediate flap. Filling isusually effected after closure of one end of the carton. Due to theadhesive disposed in the area of overhang and usually at least also atthe outer edge of the area in which the surface of the outer flapcontacts the surface of the intermediate flap, the application of heator heat and pressure to these flaps or areas produces an effective sealof the carton when the adhesive employed is thermoplastic orheat-sealing. Ordinarily the application of heat and pressure will befollowed by cooling, generally under pressure contact, to prevent theflaps from springing apart until the adhesive has set or solidified, orhas at least considerably increased in tack or viscosity, and inreference to adhesive activation provided for thermoplast c materials, Iintend that a setting step be included in practice. A similar result isproduced by the application of pressure when a pressure sensitiveadhesive is employed, the heat and/or pressure required being only thatsuflicient to activate the particular adhesive employed.Adhesiveactivating conditions may also be provided in selected cases byinfra-red rays, dielectric heating, or application of microwaves, and inselected cases the adhesive-activating conditions may be applied justbefore closing all or even any of the closure flaps rather than after.When the construction involves the use of laminated sheet material, theapplication of heat or heat and pressure or other adhesive-activatingconditions to the exposed surface of the outer flap, or to theintermediate flaps just prior to or after closing of the carton,effectively extrudes the thermoplastic adhesive laminant from therecessed edges of the intermediate flap, thereby forming a bond betweenthe inner surface of the outer flap and the upper surface of the innerflap or flaps in the area of overhang of the intermediate flap by theouter flap. As already stated, this strong edge-seal alone may in somecases be sufficient. Where an even more effective seal is desired, thesame procedure is employed except that a minimal thickness ofheat-sealing or pressure-sensitive adhe sive, as required in aparticular case, is disposed either partially or completely on thesurface of the recessed intermediate flap member which will be upwardlydisposed upon closing of the carton, or upon at least a portion of thesurface of the uter flap which will be inwardly disposed upon closing ofthe carton, or upon both said surfaces, so that upon application of heatand/or pressure an effective seal will be provided not only in the areaof overlap but also interfacially between the opposed surfaces of therecessed intermediate flap and its overlymg outer flap. Such areas ofadhesive may be conveniently printed upon or otherwise locally appliedto the selected surfaces of the carton blank. It goes without sayingthat the adhesive used for such interfacial sealing between the recessedintermediate flap and the outer flap should be heat-sealing andmoisture-proof when a substantially leakproof or moisture-vapor proofcarton is desired, which in addition requires the employment of eitherproofed or laminated sheet materials of construction.

It will be apparent that the thermoplastic or pressuresensitive adhesivemay also be disposed upon the surface of the inner flaps in the area ofoverhang of the intermediate fiap by the outer flap, for example,referring to FIGURE 4, on end flaps 233 and 234 immediately adjacentscore lines 257 and 258 and along the lateral edges thereof which willprotrude beyond the intermediate flap 232 at its longitudinal edge uponerecting of the carton and folding intermediate flaps 233 and 234inwardly, folding intermediate flap 232 in upon end flaps 233 and 234,and folding top flap 231 upon intermediate flap 232. It should also beapparent that such disposition of adhesive upon the surface of the inneror end flaps may be employed alone, as in a carton blank structure 10 ofFIGURE 3 or 4, or together with adhesive on the front top or outer flapas shown in either FIGURE 3 or 4, and is preferably employed in additionto the adhesive on the top or outer flap when a completely nonbowed andstrongly-sealed carton is desired.

While in the drawings it is indicated that thermoplastic laminantadhesive also extrudes out of the cut edges of the innermost ply of thecarton construction, and while such does ordinarily occur when sealingcartons are constructed from laminated sheet materials according to thepresent invention against a mandrel, it is to be understood thatextrusion of the adhesive from the cut edges is optional and not arequisite for satisfactory sealing of the innermost flaps, whilepreferable in some instances, of the cartons produced according to orconstituting the present invention. Moreover, while the drawings showcarton blanks having the recessed intermediate flap attached to the backface panel of the carton, the recessed intermediate flap can equallywell be attached to the front face panel of the carton and the outerflap. usually having dimensions generally approximating those of thecarton end cross-section, can equally well be attached to the back facepanel. Moreover, the recessed intermediate flap at one end of the cartonmay be attached to the front face panel while at the other end of thecarton the recessed intermediate flap may be attached to the back facepanel, and vice versa. In addition, the relieving. recessing, or cuttingback of the edges of the intermediate flap is not restricted to anyparticular geometric design or form of the intermediate flap or recess,and in one embodiment, for example, the intermediate flap may simply betapered from its juncture with its adjoining face panel to a somewhatreduced width at its outer edge.

Any or all of the sheet materials used as carton stocks may be treatedin any one of various ways, such as by printing, treating forgreaseproofness or wax hold-out, glossing, and the like, and suchtreatment will be understood to be applicable also in the case oflaminated sheet material, in which case it is ordinarily applied priorto lamination of the sheet materials. Representative sheet materialsinclude, in addition to paper and paperboard parchment papers, paperscontaining foil mounted thereon, grease-proof apers, glassine papers,non-woven fabrics, and the like. In any event, however, where laminatedsheet materials are employed, the adhesive will normally be present inan amount of at least about fifty-five and preferably at least sixtypounds per ream (24 x 36500). This is sufficient to provide a thicknessof laminant in excess of about .004 inch. With this thickness oflaminant, there is sufficient adhesive material to extrude through therecessed edges of the intermediate flap member and into the area ofopposed facing relationship between the outer flap and the inner flap orflaps in the area of overlap without bowing of the carton upon sealing.This amount of laminant is also sufficient to extrude out of the cutedges of the top or outer fiap thereby to effectively seal the same.However, it is to be understood that greater thicknesses of laminant,even exceeding the combined thickness of the base sheet materials, maybe employed if desired.

While in general it is preferred to employ a lighter sheet for theinside ply of a laminated sheet, when employed, this is not necessarilythe case, and in some applications the heavier sheet may provide theinside surface of the carton wall. At least one sheet of the laminatedsheet material must have sufficient strength to provide structuralrigidity, and ordinarily both sheets will have sufficient strength forthis purpose and will each exceed about ten pounds per inch in tensilestrength as determined by TAPPI method T404m. The thickness of the sheetmaterials employed in a laminated sheet material will generally rangefrom about .002 to about .012 inch, with a thickness of laminant fromabout .004 inch to about .015 inch, but usually ranging from about .004to 1 1 about .008 inch. While the thickness of the sheet materials ismentioned is usually from about .002 to .012 inch, I may employpaperboard sheet material, either alone or as a part of a laminatedsheet, which has a thickness as great as .03 inch.

The thermoplastic laminating adhesive employed as the laminant in suchlaminated sheet material may, for example, have a viscosity of at least75, and preferably at least 150, centipoises in the range of from aboutten degrees to about fifty degrees Fahrenheit above its softening point,e.g., at a temperature of about 220270 degrees Fahrenheit, as measuredby a Brookfield Synchroelectric viscometer or other rotationalviscometer at a spindle speed less than ten r.p.m. Hot melt compositionsbased on hydrocarbon and especially petroleum waxes are suitable,preferably those based on microcrystalline waxes. These may be increasedin viscosity by admixture therewith of polymers of ethylenicallyunsaturated hydrocarbons, natural gums, and the like, or by addition ofgelling agents, and especially by the addition of a hydrous adsorbentpowder in combination with a surface activator, especially inorganicgelling agents such as hydrated attapulgite and the like together withnitrogen-containing surface activators, especially fatty-acid amides andalkyl quaternary ammonium salts. The density of the adhesive laminantsemployed will ordinarily be from about 12 to about 25 or more pounds perream (24 X 36-500) per each .001 inch of thickness thereof.

As further representative carton stocks, suitable for carton blanks andcartons according to the present invention, may be mentioned the usualpaper or paperboard sheets, such as made on a cylinder machine or amultipleheadbox Fourdrinier machine. having a number of plies, or heavypaper sheets having only a single ply. Generally speaking, the cartonstock may be any fibrous cellulosic or synthetic sheet, but in somecases may include foils or films as one ply thereof. Aluminum foil maysometimes advantageously be used for one ply, especially when the ply isto become the inside surface of a carton. In such cases the aluminumfoil may be and preferably is mounted on a light paper before gluing orlaminating to a second fibrous ply, foil side in. For highmoisture-vapor proofncss, the carton stocks may be proofed, includingfor example dry waxed, semi-waxed, or surface waxed paperboard or papermaterials, or polyethylene-coated materials, and the like. As pointedout hereinbefore, the cartons of the invention are preferably fabricatedof laminated sheet materials, such as paperboard Wax-laminated to paper,and will in general be fibrous cellulosic or synthetic sheets laminatedto each other or to foils with suitable laminating materials ashereinafter described. It will be apparent that either laminated sheetmaterials or proofed sheet materials should be employed when a leakproofor moisture-vapor proof and especially when a hermetically sealed cartonstructure is desired.

As pressure-sensitive adhesives, which may be used in accord with thepresent invention, may be mentioned various elastomers including naturaland synthetic rubbers, chlorinated rubbers, chlorinated polyethylene,vinyl acetate, and the like, which may be suitably modified with variousresins and plasticizers, all according to conventional knowledge andprocedure of the art. These adhesives in some cases will not be normallypressure sensitive, but will become so upon application of heat or otheractivating conditions.

As thermoplastic laminant for uniting the plys of laminatcd sheetmaterials which may be employed in producing the carton blanks andcartons of the present invention, the so-called hot-melt adhesives arepreferred. Moisturevapor-proof hot melts based on petroleum waxes arepreferable, as these have a high degree of plasticity and flexibility.Hot melts based on micro-crystalline wax are especially preferred.Additional representative laminant adhesives include (A)microcrystalline waxes of any origin, e.g., Louisiana, Pennsylvania, orMid-Continent origin, and/or parafiin waxes modified with: (1) syntheticpolyiii mers such as butyl rubber, polyisobutylene, polyethylene,copolymers of vinyl acetate and ethylene, (2) aluminum stearate, (3)hydrophilic adsorbents. (4) surface activators, (5) terpene resins, (6)ester gums, (7) rosin derivatives, and the like; (B) low molecularweight polymers such as (1) polystyrene of 4,000 to 20,000 M.W., (2)polyethylene of 2,000 to 12,000 M.\V.. (3) polyterpenes, (4) isoprenepolymers, (5) chlorinated natural and synthetic rubbers, (6) naturalrubbers, and the like; (C) cellulose derivatives such as (1) ethylcellulose compositions and mixtures thereof with resins, waxes andplasticizers, (2) nitrocellulose thermoplastics, (3) cellulose acetatesor other esters and mixtures thereof with resins and the like; all ofwhich may be suitably modified with various other resins and withplasticizers, according to conventional knowledge and procedure of theart.

As heat-sealing adhesives suitable for surface disposition may bementioned the various thermoplastic hydrocarbon waxes, especiallypetroleum waxes, of paraifinic or microcrystalline nature, hydrocarbonpolymers such as polystyrene or polyethylene, ethyl cellulose hot melts,polyterpenes, rosin derivatives, and the like, which may again besuitably modified with various resins and plasticizers, all according toconventional knowledge and procedure f the art.

Evidencing the typical superiority of representative edge-seal cartonsof the present invention, the following test was conducted. Cartonblanks were cut and scored on a press to give exact duplicates, exceptthat one set of carton blanks was provided with a recessed intermediateflap while the other set had a full intermediate flap. The cartonserected therefrom were of equal dimensions, inches by 3 inches by 1%inches, and were in all respects the same, except for the said recessededge of the intermediate fiap in the one set of cartons. The material oftheir construction was a representative laminated stock consisting ofseventy pound coated Fourdrinier paper laminated to a fifty pounddry-waxed Fourdrinicr paper with eighty-five pounds per ream of thefollowing wax composition:

(a) 3% hydrogenated tallow amides containing 22% adecanamide, 75%octadecanamide, octadecenamide (Armid HT) (b) 10% powdered attapulgitehaving a particle size between .02 and two microns, an average particlesize of about .14 micron, and a 17% moisture content (Attagel 20) (c)87% Pennsylvania grade microcrystalline wax, M.P.

l160 F. (Quaker State L-500) After erection of the cartons, their bottomflaps were glued shut with moistureproof polyvinyl acetate-basedadhesive. Fifty cubic centimeters (approximately fifty grams) ofanhydrous calcium chloride was placed in each of the cartons and the topflaps closed. The cartons having the recessed intermediate flap wereglued and their ends heat sealed, while the cartons having correspondingfull glue fiaps were glued. Moistureproof polyvinylacetate-basedadhesive was employed in both cases.

The end heat-sealed cartons having the recessed intermediate ilaps andthe cartons having glued full intermediate fiaps were tested by storingunder conditions of fifty percent relative humidity and the rate oftheir weight gain measured. The average rate of weight gain of fiveboxes having the recessed intermediate flap and heat-sealed at theirends was .056 gram per day per box. The average rate of weight gain offive boxes having the full glue flap was .099 gram per day per box. Thecartons end-sealed according to the present invention were thereforeapproximately twice as effective in preventing moisture-vapor transferas the corresponding cartons made from identical sheet material buthaving a full intermediate flap instead of a recessed intermediate flap.

It is thus seen that the present invention provides a method of forminga scaled carton which includes the steps of providing a carton bodyhaving a series of end closure flaps including an outer flap, anintermediate flap recessed along an edge thereof so as to be narrower inbreadth than the outer flap along at least a portion of an edge thereof,and so as to provide an area of overhang of said intermediate flap bysaid outer flap when said flaps are folded upon each other upon closingof the carton, at least one and usually two inner flaps which provide asurface for opposed facing relation with said outer flap at a pointwhere said intermediate flap is of diminished breadth with respect tothe outer flap, providing at least one of said flaps with an adhesiveadapted to be disposed in place at least in said area of overhang (oropposed facing relationship) and to be activated upon the application ofadhesive-activating conditions to the carton exterior, folding the saidinner flap or flaps first, folding the intermediate flap into overlyingrelation upon said inner flap or flaps, and folding the outer flap intooverlying relation upon said intermediate flap, whereby the surface ofthe outer flap comes into opposed facing relation with the surface of atleast one inner flap in the area of overhang, applyingadhesive-activating conditions, optionally followed by adhesive settingconditions, to the flaps, preferably to the exterior of the carton afterclosing, and most conveniently to the outer flap thereof, to effectivelyseal said outer flap to said inner flap or flaps interfacially in saidarea of opposing facing relationship and thereby also seal off therecessed edge of the intermediate fiap. In its broader sense, thepresent invention also provides carton blanks, cartons formed therefrom,and sealed cartons, having enclosed body walls in articulation and endclosure flaps articulated to the said body walls, which said end closureflaps are adapted to be folded in sequence to form a plural layeredclosure in which the flaps lie in engagement with the surface of oneflap upon the surface of another flap, one of said flaps being an outerflap usually but not necessarily generally dimensioned to cover theentire end crosssection of the carton body, another of the said flapsbeing an intermediate flap also usually generally dimensioned to coverthe entire end cross-section of the carton body but in any event havingedge portions where the same would ordinarily be exposed in the closedcarton slightly recessed so as to extend inwardly of the correspondingedges of the outer flap, thereby forming one or more recesses or areasof overhang in said closure adapted to be filled with adhesive, and anadhesive carried by at least one of said flaps and adapted to bedisposed in said areas provided upon folding of the carton closure flapsand activated in place therein upon the application ofadhesive-activating conditions. Preferably the adhesive adapted to bedisposed and activated in place in said areas is carried as thethermoplastic laminating adhesive between plies of the laminatedintermediate flap, and extrudes outwardly of the recessed edge of theintermediate flap upon the application of heat or heat and pressure tothe flaps, usually to the carton exterior and most conveniently to theouter flap thereof, to later congeal and thereby effect a seal betweenthe surface of the outer flap and the surface of the inner flap by meansof said extruded thermoplastic adhesive laminant, thereby also sealingoff the cut edge of the said intermediate flap without disposing any orsubstantially any of the thermoplastic laminant adhesive upon theexterior exposed faces of the carton.

It is to be understood that the invention is not limited to the exactdetails of construction, operation, or exact materials shown anddescribed, as obvious modifications and equivalents will be apparent toone skilled in the art, and the invention is therefore to be limitedonly by the scope of the appended claims.

I claim:

1. A carton blank having at least one series of end closure flaps,including an inner flap, a full outer flap, and an intermediate flaphingedly connected to a panel of said carton positioned opposite to thepanel to which said outer flap is connected when said carton is erected[and an outer flap,] said flaps being adapted to be folded in sequenceupon erecting a carton from said blank and closing of the same toprovide a plural layered closure in which the flaps lie with the surfaceof one flap upon the surface of another flap, said intermediate flapbeing recessed along at least one [an] edge thereof so as to be narrowerthan said outer flap along at least a portion of at least one [an] edgethereof, and so as to provide an area of overhang of said intermediateflap along at least one transverse side thereof perpendicular to itsfold line by said outer flap when said flaps are folded upon each otherupon closing of the carton, said intermediate flap being ofapproximately the same dimensions as said outer flap except for recessedarea, said inner flap providing a surface for opposed facing relationwith said outer flap adjacent the fold line of said inner flap in saidarea of overhang upon erection of a carton from said blank and closingof the same, at least one of said flaps being provided with adhesiveadapted to be disposed and activated in said area of overhang upon theerection of a carton from said blank and closing and sealing thereof bythe application of adhesive-activating conditions to the flap carryingsaid adhesive, the amount of said adhesive being sufficient to securesaid outer flap to said inner flap in said area of overhang.

2. A carton blank accoring to claim 1, wherein the adhesive is selectedfrom heat-sealing, thermoplastic, and pressure-sensitive adhesives, andis carried on the surface of at least one of the outer and inner flapsin the area of their opposed facing relationship in a carton erectedfrom said blank.

3. A carton blank of laminated sheet material in which the laminant is athermoplastic adhesive laminant, said blank having at least one seriesof end closure flaps including an inner flap, an intermediate flap, andan outer flap, said flaps being adapted to be folded in sequence uponerecting a carton therefrom and closing of the same to provide a plurallayered closure in which the flaps lie with the surface of one flap uponthe surface of another flap, said intermediate flap being recessed alongan edge thereof so as to be narrower than said outer flap along at leasta portion of an edge thereof, and so as to provide an area of overhangof said intermediate flap by said outer flap when said flaps are foldedupon each other upon closing of the carton, said inner flap providing asurface for opposed facing relationship with said outer flap adjacentthe fold line of said inner flap in said area of overhang upon erectionof a carton from said blank and closing of the same, said thermoplasticadhesive laminant in said intermediate flap being sufficient and adaptedto be extruded through the recessed edge thereof into said area ofoverhang upon the erection of a carton from the said blank and closingand sealing thereof by the application of thermoplastic laminantadhesive-activating conditions to said intermediate flap and allowingthe said laminant to congeal.

4. A carton blank according to claim 3, wherein the thickness of thelayer of adhesive laminant in the laminated sheet material from whichthe carton blank is constructed is at least about .004 inch.

5. A carton blank according to claim 3, wherein the thermoplasticadhesive laminant of the laminated sheet material from which the cartonis constructed is present in an amount of at least about fifty-fivepounds of laminant per ream of sheet material.

6. An erected and sealed carton including a carton body having a seriesof closure flaps at an end thereof, including an inner flap, a fullouter flap, and an intermediate flap hingedly connected to a panel ofsaid carton positioned opposite to the panel to which said outer flap isconnected, [and an outer flap,] said flaps being folded to provide aplural layered closure in which the flaps lie with the surface of oneflap upon the surface of another flap, said intermediate flap beingrecessed along both [a] side edges [edge] thereof so as to be narrowerthan said outer flap along at least a portion of both [a] side edges[edge] thereof, and so as to provide an area of overhang of saidintermediate flap by said outer flap along both transverse sides thereofperpendicular to its fold line, said intermediate flap being ofapproximately the same dimensions US said outer flap except for recessedarea, said inner flap providing a surface for opposed facing relationwith said outer flap adjacent to the fold line of said inner flap insaid area of overhang, and an adhesive in said area of overhangintcrfacially bonding said inner flap to said outer flap and sealing offthe recessed edges [edge] of said intermediate flap, said adhesive beingprovided in said area of opposed facing relationship and beingsubstantially absent from the exterior exposed faces of the carton.

7. A carton according to claim 6, wherein the adhesive is selected fromheat-scaling, thermoplastic, and pressure-sensitive adhesives, and iscarried on the surface of at least one of the outer and inner flaps inthe area of their opposed facing relationship.

8. A carton according to claim 6, wherein additional adhesive isprovided intcrfacially between said intermediate and top flaps.

9. An erected and sealed carton of laminated sheet material in which thelaminant is a thermoplastic adhesive laminant. including a carton bodyhaving a series of closure flaps at an end thereof, including innerflaps, a fall outer flap, and an intermediate flap hingcdly connected toa panel of said carton positioned opposite to the panel to which saidouter flap is connected, [and an outer flap,] said flaps being folded toprovide a plural layered closure in which the flaps lie with the surfaceof one flap upon the surface of another flap, said intermediate flapbeing recessed along both side edges thereof so as to be narrower thansaid outer flap along at least a portion of both side edges thereof, andso as to provide an area of overhang of said intermediate flap by saidouter flap on both sides thereof perpendicular to its fold line, saidintermediate flap being of approximately the same dimensions as saidouter flap except for recessed areas, said inner flaps providing asurface for opposed facing relation with said outer flap in said areasof overhang, and an adhesive in said area [areas] of opposed facingrelationship interfacially bonding said inner flap to said outer flapadjacent the fold lines of said inner flaps and sealing off the recessededges of said intermediate flap, said adhesive comprising thermoplasticlaminant adhesive carried between the plies of sheet material of saidintermediate flap and extruded outwardly from the recessed edges of saidintermediate flap and thus provided in said area [areas] of opposedfacing relationship, said thermoplastic adhesive laminant beingsubstantially absent from the exterior exposed faces of the carton.

10. A carton according to claim 9, wherein the thickness of the layer ofadhesive laminant in the laminated sheet material from which the cartonis constructed is at least about .004 inch.

11. A carton according to claim 9, wherein the thermoplastic adhesivelaminant of the laminated sheet material from which the carton isconstructed is present in an amount of at least about titty-five poundsof laminant per ream of sheet material.

12. A carton according to claim 9, wherein additional adhesive isprovided interfacially between said intermediate and top flaps.

13. An erected and sealed carton of laminated sheet material in whichthe laminant is a thermoplastic adhesive laminant, including a cartonbody having a series of closure flaps at an end thereof, including aninner fiap, an intermediate flap, and an outer flap, said flaps beingfolded to provide a plural layered closure in which flaps lie with thesurface of one flap upon the surface of another flap, said intermediateflap being recessed along an edge thereof so as to be narrower than saidouter flap along at least a portion of an edge thereof, and so as toprovide an area of overhang of said intermediate flap by said outerflap, said inner flap providing a surface for opposed facing relationwith said outer flap in said area of overhang, and adhesive in said areaof opposed facing relationship interfncially bonding said inner flap tosaid outer flap and sealing off the recessed edge of said intermediateflap, substantially filling said area of overhang, and beingsubstantially absent from the exterior exposed faces of the carton.

14. An erected and sealed carton of laminated sheet material, comprisinga carton body having a series of closure flaps at one end thereof,including an inner flap, an intermediate flap, and an outer flap, saidflaps being folded to provide a plural layered closure in which theflaps lie with the surface of one flap upon the surface of another flap,said intermediate fiap having a cut-away portion so as to provide anarea of opposed facing relation between said inner flap and said outerflap, and a thermoplastic adhesive in said area of opposed facingrelation interfacially bonding said inner flap to said outer flap andsealing the cut edge of said intermediate flap, said adhesive havingbeen carried between the plies of the sheet material of saidintermediate flap and having been extruded from the cut edge of saidintermediate flap and thus having been provided in said area of opposedfacing relation, said adhesive being substantially absent from theexterior exposed faces of the carton.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,341,845 2/1944 Mark. 2,348,687 5/1944 Abrams.2,412,031 12/1946 Bergsteirn. 2,439,435 4/1948 Richardson. 2,441,477 5/1948 Farrell. 2,496,043 1/1950 Farrell. 2,521,208 9/1950 Eaton.2,530,787 11/1950 Sanford. 2,550,520 4/ l 951 Bennett. 2,670,128 2/1954Stowitts.

DAVIS T. M OORHEAD, Primary Examiner.

